Fabrication and Soft-X-Ray and EUV Range Testing of Au- and Multilayer Mo/Si-Coated Diffraction Gratings with High-Order Blaze

— Blazed and low-roughness 500 lines/mm diffraction gratings, designed for operation in high orders in the soft X-ray and extreme UV (EUV) radiation ranges and having Au and multilayer Mo/Si coatings, have been fabricated by wet anisotropic etching of Si(111)4° vicinal wafers and investigated by atomic force and scanning electron microscopy. The diffraction efficiency of the gratings was determined both using a laboratory reflectometer and by modeling based on a rigorous method of boundary integral equations in the PCGrate™ code, taking into account realistic groove profiles. The diffraction efficiency values measured in unpolarized light with wavelengths of 13.5 and 4.47 nm and the calculated values, found with allowance for random roughness, are almost the same. The absolute efficiency of the grating with a multilayer (five Mo/Si bilayers) coating with a period of 20 nm is ~40% in the –8th diffraction order at an angle of incidence of 70.5°, which is a record value for a high-order mid-frequency grating.